redo LNWorker pay:

- wait until htlc has been fulfilled
 - raise if htlc is not fulfilled
 - return boolean success
 - try multiple paths in GUI

electrum/commands.py

@@ -785,8 +785,7 @@ class Commands:
 
     @command('wn')
     def lnpay(self, invoice):
-        addr, peer, f = self.lnworker.pay(invoice)
-        return f.result()
+        return self.lnworker.pay(invoice, timeout=10)
 
     @command('wn')
     def addinvoice(self, requested_amount, message):

electrum/gui/qt/main_window.py

@@ -1674,33 +1674,25 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
 
     def pay_lightning_invoice(self, invoice):
         amount = self.amount_e.get_amount()
-        LN_NUM_PAYMENT_ATTEMPTS = 1  # TODO increase
-
+        LN_NUM_PAYMENT_ATTEMPTS = 3
         def on_success(result):
             self.logger.info(f'ln payment success. {result}')
             self.do_clear()
         def on_failure(exc_info):
             type_, e, traceback = exc_info
             if isinstance(e, PaymentFailure):
-                self.show_error(_('Payment failed. Tried {} times:\n{}')
-                                .format(LN_NUM_PAYMENT_ATTEMPTS, e))
+                self.show_error(_('Payment failed. {}').format(e))
             elif isinstance(e, InvoiceError):
                 self.show_error(_('InvoiceError: {}').format(e))
             else:
                 raise e
         def task():
-            failure_list = []
             for i in range(LN_NUM_PAYMENT_ATTEMPTS):
-                try:
-                    addr, peer, future = self.wallet.lnworker.pay(invoice, amount_sat=amount)
-                    future.result()
+                success = self.wallet.lnworker.pay(invoice, amount_sat=amount, timeout=30)
+                if success:
                     break
-                except PaymentFailure as e:
-                    failure_list.append(e)
-                    # try again
             else:
-                msg = '\n'.join(str(e) for e in failure_list)
-                raise PaymentFailure(msg)
+                raise PaymentFailure('Failed after {i} attempts')
 
         msg = _('Sending lightning payment...')
         WaitingDialog(self, msg, task, on_success, on_failure)

electrum/lnpeer.py

@@ -973,7 +973,7 @@ class Peer(Logger):
     @log_exceptions
     async def _on_update_fail_htlc(self, chan, htlc_id, local_ctn):
         await self.await_local(chan, local_ctn)
-        self.network.trigger_callback('ln_message', self.lnworker, 'Payment failed', htlc_id)
+        self.lnworker.pending_payments[(chan.short_channel_id, htlc_id)].set_result(False)
 
     def _handle_error_code_from_failed_htlc(self, error_reason, route: List['RouteEdge'], channel_id, htlc_id):
         chan = self.channels[channel_id]
@@ -1117,7 +1117,7 @@ class Peer(Logger):
     @log_exceptions
     async def _on_update_fulfill_htlc(self, chan, htlc_id, preimage, local_ctn):
         await self.await_local(chan, local_ctn)
-        self.network.trigger_callback('ln_message', self.lnworker, 'Payment sent', htlc_id)
+        self.lnworker.pending_payments[(chan.short_channel_id, htlc_id)].set_result(True)
         self.payment_preimages[sha256(preimage)].put_nowait(preimage)
 
     def on_update_fail_malformed_htlc(self, payload):

electrum/lnworker.py

@@ -314,6 +314,7 @@ class LNWallet(LNWorker):
             c.set_local_commitment(c.current_commitment(LOCAL))
         # timestamps of opening and closing transactions
         self.channel_timestamps = self.storage.get('lightning_channel_timestamps', {})
+        self.pending_payments = defaultdict(asyncio.Future)
 
     def start_network(self, network: 'Network'):
         self.network = network
@@ -641,14 +642,15 @@ class LNWallet(LNWorker):
         chan = f.result(timeout)
         return chan.funding_outpoint.to_str()
 
-    def pay(self, invoice, amount_sat=None):
+    def pay(self, invoice, amount_sat=None, timeout=10):
         """
-        This is not merged with _pay so that we can run the test with
-        one thread only.
+        Can be called from other threads
+        Raises timeout exception if htlc is not fulfilled
         """
-        addr, peer, coro = self.network.run_from_another_thread(self._pay(invoice, amount_sat))
-        fut = asyncio.run_coroutine_threadsafe(coro, self.network.asyncio_loop)
-        return addr, peer, fut
+        fut = asyncio.run_coroutine_threadsafe(
+            self._pay(invoice, amount_sat),
+            self.network.asyncio_loop)
+        return fut.result(timeout=timeout)
 
     def get_channel_by_short_id(self, short_channel_id):
         with self.lock:
@@ -656,15 +658,14 @@ class LNWallet(LNWorker):
                 if chan.short_channel_id == short_channel_id:
                     return chan
 
-    async def _pay(self, invoice, amount_sat=None, same_thread=False):
+    async def _pay(self, invoice, amount_sat=None):
         addr = self._check_invoice(invoice, amount_sat)
         self.save_invoice(addr.paymenthash, invoice, SENT, is_paid=False)
         self.wallet.set_label(bh2u(addr.paymenthash), addr.get_description())
         route = await self._create_route_from_invoice(decoded_invoice=addr)
-        peer = self.peers[route[0].node_id]
         if not self.get_channel_by_short_id(route[0].short_channel_id):
             assert False, 'Found route with short channel ID we don\'t have: ' + repr(route[0].short_channel_id)
-        return addr, peer, self._pay_to_route(route, addr, invoice)
+        return await self._pay_to_route(route, addr, invoice)
 
     async def _pay_to_route(self, route, addr, pay_req):
         short_channel_id = route[0].short_channel_id
@@ -674,6 +675,8 @@ class LNWallet(LNWorker):
         peer = self.peers[route[0].node_id]
         htlc = await peer.pay(route, chan, int(addr.amount * COIN * 1000), addr.paymenthash, addr.get_min_final_cltv_expiry())
         self.network.trigger_callback('htlc_added', htlc, addr, SENT)
+        success = await self.pending_payments[(short_channel_id, htlc.htlc_id)]
+        return success
 
     @staticmethod
     def _check_invoice(invoice, amount_sat=None):

electrum/tests/regtest/regtest.sh

@@ -101,7 +101,7 @@ if [[ $1 == "redeem_htlcs" ]]; then
     sleep 10
     # alice pays bob
     invoice=$($bob addinvoice 0.05 "test")
-    $alice lnpay $invoice
+    $alice lnpay $invoice || true
     sleep 1
     settled=$($alice list_channels | jq '.[] | .local_htlcs | .settles | length')
     if [[ "$settled" != "0" ]]; then

electrum/tests/test_lnpeer.py

@@ -90,6 +90,7 @@ class MockLNWallet:
         self.inflight = {}
         self.wallet = MockWallet()
         self.localfeatures = LnLocalFeatures(0)
+        self.pending_payments = defaultdict(asyncio.Future)
 
     @property
     def lock(self):
@@ -216,25 +217,12 @@ class TestPeer(SequentialTestCase):
         w2.invoices[bh2u(RHASH)] = (pay_req, True, False)
         return pay_req
 
-    @staticmethod
-    def prepare_ln_message_future(w2 # receiver
-            ):
-        fut = asyncio.Future()
-        def evt_set(event, _lnwallet, msg, _htlc_id):
-            fut.set_result(msg)
-        w2.network.register_callback(evt_set, ['ln_message'])
-        return fut
-
     def test_payment(self):
         p1, p2, w1, w2, _q1, _q2 = self.prepare_peers()
         pay_req = self.prepare_invoice(w2)
-        fut = self.prepare_ln_message_future(w2)
-
         async def pay():
-            addr, peer, coro = await LNWallet._pay(w1, pay_req, same_thread=True)
-            await coro
-            print("HTLC ADDED")
-            self.assertEqual(await fut, 'Payment received')
+            result = await LNWallet._pay(w1, pay_req)
+            self.assertEqual(result, True)
             gath.cancel()
         gath = asyncio.gather(pay(), p1._message_loop(), p2._message_loop())
         async def f():